The present invention relates to a fluid expander and, in particular, to a rotary fluid expander having an adjustable configuration.
Internal combustion engines are commonly used in various applications to generate electrical or mechanical power. For example, internal combustion engines have been used in automobiles and other vehicles, electrical generators, lawn mowers, pumps, etc. While suitable for their conventional uses, internal combustion engines produce objectionable exhaust gases, even when expensive pollution control devices are utilized, require periodic servicing to prevent build-up of deposits caused by the combustion of fuel, require heavy engine blocks in order to contain the explosion of fuel and safely convert its force into useful mechanical motion, and may, due to the sequential firing of individual cylinders, require the use of a heavy flywheel to provide a smooth flow of power.
As an alternative to internal combustion engines, gas turbines are employed in various applications. For example, gas turbines are used to generate electrical power, and they have also been used to power vehicles and airplanes. Gas turbines have not been commonly used for vehicular and stationary applications because the extremely high rotor speeds used to achieve efficiency lead to a potential safety hazard in case of rotor failure. High speeds also require extensive gear reductions to reduce turbine output speeds to usable speeds.
Most internal combustion engines and gas turbines are powered by fossil fuels. Because the world's supply of fossil fuels is finite, alternatives such as systems that generate power from solar radiation and geothermal energy have been investigated. These systems develop energy, for example, by transferring heat energy to a working fluid, pressurizing the fluid based on the transferred heat energy, and obtaining work from the pressurized fluid via a fluid expander. However, solar and geothermal systems typically generate working fluid pressures too low to efficiently power conventional fluid expanders, thereby limiting usefulness of solar and geothermal energy sources.
Fluid expanders have been proposed in which pistons are reciprocated in cylinders while rotating around a drive shaft to power the drive shaft. Fluid expanders may utilize external combustion, useful for solar or geothermal systems, or internal combustion, useful for gasoline or diesel systems. U.S. Pat. Nos. 839,300; 980,481; 1,345,808; 3,654,906; 3,695,237; 3,939,809; 3,968,776; 4,779,579; 5,070,825; 5,094,195; 5,253,473; and 5,285,633 disclose various rotary fluid expander designs, both external and internal combustion. A drawback of these devices is that the performance characteristics of the devices are limited by the fixed nature of the structure of the devices. For example, in order to obtain a full range of torque and speed from these devices, a gearing reduction system such as a transmission is required, which can be complicated and costly.